1. Technical Field
The present invention relates to a forwarding system that includes a plurality of packet forwarding devices forming a redundant group based on a redundancy protocol such as a VRRP (Virtual Router Redundancy Protocol) or the like. More specifically, the present invention relates to controlling of operation mode of a packet forwarding device in backup operation.
2. Background Art
A VRRP is a protocol to achieve redundancy of routers that perform IP (Internet Protocol) packet forwarding (see Japanese Unexamined Patent Application Publication Nos. 2004-266819, 2006-310976 and 2007-318263, for example). Routers that support the VRRP form a redundancy group called VRRP group, and behave as one virtual router. In the VRRP group, one router functions as an active system router (called master router) that performs packet forwarding, and other routers function as standby system routers (called backup routers).
In the event of a failure occurrence in the master router, the backup router turns into a master router and takes over IP packet forwarding processing. The backup router should constantly perform standby operation so as to be able to take over the IP packet forwarding processing as soon as the failure occurs in the master router. In summary, the backup router constantly monitors the control packet (more specifically VRRP advertisement) periodically transmitted by the master router, and turns into the master router when the VRRP advertisement cannot normally be received.
As stated above, the backup router must constantly monitor the VRRP packets. Further, in order to promptly take over the processing of the master router, hot standby is required to operate a plurality of communication ports, a packet forwarding function unit, a control unit that performs updating of a routing table and an ARP table or the like in a conduction state. However, a case may also be considered in which important communication is rarely occurred in a certain time period (nighttime, for example) depending on the environments where the routers are used. As the backup router constantly performs hot standby in the VRRP, it is difficult to reduce power consumption.
Note that the above-mentioned problem is not limited to the VRRP and routers forwarding the IP packet. It is a typical problem when employing a redundancy protocol in which a plurality of packet forwarding devices form a redundancy group and transmission of a control packet by one packet forwarding device that performs active system operation (master operation) controls switching of another packet forwarding device that performs standby system operation (backup operation) to the active system operation.